This application is a continuation-in-part of my prior application Ser. No. 633,508, filed July 23, 1984.
This invention relates generally to metal powder consolidation as applied to one or more metallic bodies, and more particularly to joining or cladding of such bodies employing powdered metal consolidation techniques.
As described in U.S. Pat. Nos. 3,356,496 and 3,689,259, it is known to utilize a pressurizing medium consisting of refractory particulate matter and high temperatures to consolidate (or densify) a metallic object. In this approach, the pressure applied by a press is transmitted through a hot ceramic particle bed to the hot preformed part having a density less than that of its theoretical density. The pressurization of the part occurring in all directions causes voids, gaps or cavities within the part to collapse and heal, the part being densified to a higher density which may be equal to its theoretical density.
Conventional powder metallurgy techniques are limited to the production of parts having shapes that can be produced by closed die pressing in forming of the powder preform. Attempts to produce more complex shapes having 100% density have required the use of lengthy canning procedures to protect the part from the pressurizing gas. Another approach to powdered metal consolidation utilizes preforms requiring no canning in HIP (i.e. hot isostatic pressing) yet it is limited to the shapes that can be produced by powder pressing in a die. In all cases, the preform consolidation takes place in a gas pressurized autoclave (HIP) which, as mentioned earlier, is suitable for consolidation or products whose properties are not sensitive to long time exposures to high temperatures.
It is seen, therefore, that development of a practical powdered metal process able to consolidate 100% dense shapes, too complex to produce by die pressing, utilizing short time high temperature exposure and without the need for canning would satisfy a need existent in the metal forming industry. Such a process would also meet the need for substantially lower parts costs. Prior patents relating to the subject of isostatic pressing of metal workpieces teach that if the parts being consolidated, or to be joined, have cavities or cracks or clearances between the pieces accessed by the pressurizing gas, complete densification can not take place. Parts to be consolidated or joined must, therefore, be isolated from the pressurizing gas by an impermeable casing.